Powered surgical tools are utilized extensively in modern surgery. Typically, these tools include a handpiece which houses a motor. A cutting accessory is secured to the handpiece for accomplishing a specific medical task. Some powered surgical tools are provided with drills or burrs for cutting bores into bone or hard tissue or for selectively removing portions thereof, such as bone graft harvesting. Still other powered surgical tools are provided with cutting accessories such as saw blades for separating large sections of hard tissue. The ability to use powered surgical tools has lessened the physical strain on physicians and other personnel when performing medical procedures on a patient. Moreover, most surgical procedures can be performed more quickly and more accurately with powered surgical tools than with the manual equivalents that preceded them.
In some types of conventional powered surgical tools, the cutting accessory is mounted within an attachment, and the cutting accessory and attachment are then secured to the powered handpiece. Such an arrangement is manufactured by the instant assignee and incorporates therein a ball-detent arrangement for axially positioning a cutting accessory, such as a router. This arrangement includes the cutting accessory having a concave annular groove which cooperates with balls located in the attachment in surrounding relation with the cutting accessory. A collar is provided on the attachment which is manipulated by the user to load and unload the cutting accessory. With this attachment, the collar is set to the “run” position, and the cutting accessory is inserted into the attachment until the balls seat within or “find” the accessory groove. The attachment and cutting accessory are then installed on the handpiece by manipulating a collar provided on the handpiece. The attachment is removed from the handpiece by again manipulating the handpiece collar, and then the cutting accessory is removed from the attachment by setting the attachment collar to the “unlock” position. A disadvantage of this arrangement is that the user must manually manipulate two collars during assembly. That is, one collar must be used to lock the attachment to the handpiece, and another collar must be used to position the cutting accessory relative to the attachment.
Another type of conventional powered handpiece manufactured by the assignee is a bone cutter saw chuck assembly including a receptacle for receiving a cutting accessory and a set screw. A screw driver is utilized to rotate the set screw to fixedly mount the cutting accessory in the receptacle. While this arrangement works reasonably well for its intended purpose, the set screw, being a separate component from the chuck assembly, can be lost. Further, the user must remember to sterilize the screw driver in addition to the other components.
Further, the conventional powered handpiece has a single motor that includes a bronze bushing as a rotary bearing and a pair of eccentric output drivers with roller bearings. The motor rotationally drives first ends of the drivers. Second ends of the output drivers are received in a channel of an oscillator. The ends of the eccentric output drivers move about a path and, in combination, pivotally oscillate the oscillator about an axis. The oscillator then oscillates a bone plug cutter located in a chuck to provide a bone cutting operation.
The use of two eccentric output drivers with roller bearings in the handpiece can create heat, and thus wear, which may lead to more frequent repair and/or replacement costs.
In order to address the above problems, or at least minimize the above shortcomings of the known arrangements, a chuck assembly is provided having a collar that is movable against a spring force to enable access to the chuck by a cutting accessory, and which collar is releasable to lock the cutting accessory in the chuck. Further, the handpiece includes a single output driver arrangement, which utilizes an eccentric rotary shaft to provide an oscillating motion for the cutting accessory.